To investigate the efficacy of r-metHuBDNF (25 and 150 ug/day) on survival, free from permeanent assisted ventilation (PAV), in subjects with ALS when administered by continuous intrathecal infusion for 18 months. Ventilation will be considered permeant when employed >22 hurs a day for >14 consecutive days and defined retrospectively as the beginning of that 14 day period.